The CPU industy is working on 16nm chips to debut by around 2013, but how much smaller can it go? According to the smart guys, not much smaller, stating that at 11nm they hit a problem relating to a 'quanting tunneling' phenomena. So what's next? Yes, they can still add core after core, but this might reach a plato by around 2020.
AMD's CTO predicts the 'core wars' will subside by 2020 (there seems to be life left in adding cores as Intel demonstrated a few days ago, the feasibility of a 1000 core processor.) A Silicon.com feature discusses some potential technologies that can enhance or supersede silicon.